Audi A6 3.0tdi air bubles in fuel line

[manniakk]

hello, i have a problem with 2006 audi a6 3.0 tdi. Recently i had injectors refurbished. The car was running fine but there was smoke from the exhaust. We changed the injectors and the smoke is gone but exactly after that a problem with air in the fuel occurred. If you push the car on 3-4gear above 3000rpm the car gets unresponsive and there is lack of power, when i pop the hood there are bubbles in the fuel pipe. When driving the car in the city there are no problems at all, this occurs only above 80kmh and above 3000rpm. The fuel filter was changed 4000km ago with audi oem filter. I had doubts about the fuel return lines from the injectors.I guess the o-rings that are on the injectors are not high quality, but they are not leaking fuel. Is it possible that they leak air in the system on high load? Should i try another filter and change the black valve above the filter. The pipes in the engine compartment seems well and not leaking. In it possible that the filter in the tank got clogged and the pump is not generating enough pressure? An suggestions are welcome

P.S. The car starts fine, no matter how long it stood...

[MarkTM]

A VCDS scan looks a good place to start.

[zollaf]

air bubbles mean that air is being sucked in somewhere. possibly from a connection on a filter, maybe further back. you need to find it and cure it and then it should be alright.

[manniakk]

There are no trouble codes at all. I`ve changed the o-rings on the return line and no change. Tomorrow i`ll change the fuel filter again and i`ll order the preheater valve and i`ll hope that this will fix it